Several notable features of Flatbush Gardens, a 59-building rental complex in East Flatbush, Brooklyn, are missing from its inviting ads, which show comely young couples enjoying life there. Among the site’s woes: dried feces and toilet paper carpet some basements, unleashing an unholy stink; one of its owners, David Bistricer, is on the New York City public advocate’s “worst landlords” list; and it has 8,100 outstanding building violations, 400 of which have been added in the past two months. . . . In October, the workers filed a complaint with the Occupational Saftey and Health Administration, citing conditions like overflowing raw sewage, leaking overhead waste pipes and vermin infestations.